This document only describes modifying sendmail. Many people prefer qmail.
Out of the box, sendmail does not come with the "pipe to program" feature enabled. Rightly so, this feature is a security risk. It enambles users to have their mail fed to a program instead of appended to a file. (Users can configure this in thier .forward file.)
Please don't believe me. Test your own system first. Much of this chapter might not be needed by you.
IMHO, sendmail installs with woefully insufficient documentation.
http://www.sendmail.org/ ca/email/doc/op-sh-5.html describes the syntax of sendmail.cf. I hope you don't have to use it.
This is a description of the features you are trashing in sendmail.mc http://www.sendmail.org/m4/features.html
Sendmail has a man page...
man sendmail
To get the "pipe to program" stuff in the aliases file to work
you need to modify the default sendmail.cf (by modifying the
sendmail.mc) so that the restricted shell is not used. I
suppose the proper solution would be to add the one program
to the restricted shell list, but their was no man page
on smrsh. Strangely, uncommenting the smrsh feature didn't
work, I needed to change the shell from /usr/sbin/smrsh
to /bin/bash. Yeah, this is slightly risky, but
it was not an issue on my machine. Without
this change I kept getting a "Service unavailable" error
message in the /var/log/maillog file.
The header of /etc/senmail.mc of RedHat-6 has a bug. The proper
command line is...
m4 /etc/sendmail.mc >/etc/sendmail.cf
sendmail.mc. Hopefully,
RedHat will extend the super cool Makefile idea in /etc/mail
You will need to install sendmail-cf.something.rpm first.
e.g. ...
rpm -i sendmail-cf-8.9.3-10.i386.rpm
Whenever you modify the sendmail.cf file, you should restart sendmail...
/etc/rc.d/init.d/sendmail restart
Instead of creating a new user account, we will only create an alias.
When modifying the /etc/aliases file, the double quotes
are required. There cannot be a space between the
first double quotes and the | (pipe) character, or
sendmail will complain "User unknown"
Add a line like ...
confctrl: "| /usr/local/bin/mail2news.pl ietf.confctrl "
Whenever you modify the /etc/aliases file you need to
notify sendmail.
sendmail -bi
Check the /var/log/maillog to see if it worked, or for error messages. I found it useful to open up another terminal (ssh) window to watch the log with
tail -f /var/log/maillog
If you are having trouble, and create an e-mail alias with a
different (simpler) target program to test it, remember that sendmail
runs the program as an unprivledged user, who probably doesn't
have privledges to write anywhere except globally writable directories
such as /tmp.